SHORT-TERM AND LONG-TERM BORROWINGS - Long Term Debt Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Sep. 30, 2021 USD ($) Period $ / shares shares	Sep. 30, 2020 USD ($)
Debt Instrument [Line Items]
Subordinated debentures, net of issuance costs	$ 73,980	$ 73,807
First Midwest Financial Capital Trust I
Debt Instrument [Line Items]
Equity method investment, ownership percentage	100.00%
Issuance of trust preferred securities (in shares) \| shares	10,000
Number of authorized shares of trust preferred securities issued (in shares) \| shares	10,310
Number of consecutive semi-annual periods that interest payments on capital securities may be deferred \| Period	10
Redemption price per capital security (in dollars per share) \| $ / shares	$ 1,000
First Midwest Financial Capital Trust I \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.75%
Effective interest rate	3.93%	4.01%
5.75% Fixed to Floating Rate Subordinated Debt, Due August 15, 2026 \| Subordinated debentures
Debt Instrument [Line Items]
Cash acquired due to acquisition	$ 75,000
Interest rate, stated percentage	5.75%
Net proceeds from issuance of debt, before issuance costs	$ 73,900
Subordinated debentures, net of issuance costs	74,000
Debt issuance costs	$ 1,000
Weighted Average \| First Midwest Financial Capital Trust I \| LIBOR
Debt Instrument [Line Items]
Effective interest rate	12.50%
Crestmark Bancorp, Inc.
Debt Instrument [Line Items]
Effective interest rate	3.13%
Long-term borrowings	$ 3,400
Debt instrument, term	30 years
Crestmark Bancorp, Inc. \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.00%

Number of trust preferred securities issued.

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Refers to the number of authorized shares of trust preferred securities issued by the entity.

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This element represents number of consecutive semi-annual periods that interest payment may be deferred.

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Proceeds from Issuance of Debt, Before Expenses and Underwriting Discounts and Commissions

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- Definition

Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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Carrying value as of the balance sheet date of collateralized/uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Subordinated debt places a lender in a lien position behind the primary lender of the company.

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Amount to be paid per share that is classified as temporary equity by entity upon redemption. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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